In an optical information recording/reproducing apparatus, in which two sets of circuits (including a comparator 104 and a time counting device 105 (i.e., pulse width detector), and a comparator 110 and a time counting device 111 (i.e., pulse width detector)) are provided for detecting that the fluctuation larger than a comparison level continues in the TE signal for a time period, each being set at the respective comparison level and the time duration, differently, thereby the operation of write or erase onto an optical disc 101 is stopped even if only one of them is detected. Also, a position or location information in the PID portion to be reproduced, being outputted from a PID register 107, and a location information which is read out by the PID decoder 106 are compared by a comparator 108, thereby stopping the operation of write or erase onto the optical disc 101 if they are inconsistent with.